The purpose of this project is to investigate, in analytic studies, the etiologies of selected cancers. Specific cancer sites and hypotheses are selected for which the need for investigation is clear but which have been difficult to study elsewhere. Case-control studies either recently completed or in progress include studies of the following sites or types: breast cancer, childhood and adult bladder cancer, colorectal cancer, cutaneous T-cell lymphomas, non-Hodgkin's lymphoma, leukemia, multiple myeloma, nasal cancer, testicular cancer, mesothelioma, intraocular melanoma, ovarian cancer, cervical cancer and choriocarcinoma. The studies focus either on tumors that have not been studied analytically before (e.g., because of the rarity of the tumor) or on hypotheses that are difficult to assess (e.g., because of the prevalence of the exposure or the need to detect an effect at low levels of exposrue). Since these studies are often the first or most thorough to date, they collect data on a wide range of exposures, usually from interviews and medical records.